The invention relates to a method for continuously producing, preferably for the food industry, a conversion product preferably having adhesive properties and to a conversion device for carrying out a method of this kind.
In the food industry, the chemical industry, the paper-processing industry, and the laundry industry, starch-containing suspensions are fed during their processes, the starch gelatinizing through water and increased temperature. For example, potato starch gelatinizes starting at 62.5° C., whereas wheat starch gelatinizes starting at 67.5° C. The stiffening capacity of starch glue varies depending on the type of starch.
In practice, the production of starch glue (gelatinized suspension) is problematic and procedurally complex because upon contact of not yet gelatinized starch with hot water, boundary surfaces are immediately formed that prevent a continued infiltration of water (gel blocking), causing undesired clumping.
As a consequence, the gelatinization process is divided into multiple partial steps in current practice, a first step usually consisting of mixing starch powder with water below the gelatinization temperature (gelling temperature), followed by heating the powder/water mixture in a second step (heating step) by introducing heat, such as by heat transfer at a heat transfer surface or by introducing steam. These processes are carried out batch-wise or continuously.
For instance, a two-step method of this kind for producing starch glue is known from EP 0 333 674 A2, which comprises cold pre-mixing and a heating step by steam injection under pressure. A two-step method is also described in U.S. Pat. No. 7,930,911 B1, wherein the heating takes place in a heat exchanger in this case.
Alternatively, hot water can also be provided first and the starch powder is slowly introduced while stirring vigorously. In this case, continuous operation is not possible.
EP 0 041 669 A1 describes a method for heating a starch suspension under pressure and subsequent relaxation.